1. Field of the Invention
This invention relates to connector assemblies for electrically and mechanically connecting one printed circuit board to another and, in particular, to connector assemblies having blade-like terminals for engaging cantilever beam terminals for electrically and mechanically connecting one printed circuit board to another.
2. Description of Related Art
The telecommunication and personal computer industries are progressing towards smaller portable products. At the same time, they demand the cost savings offered by surface mount technology.
Initially, the connector industry developed surface mount connectors around the 2.54 mm (0.1 inch) standard spacing or footprint typical of many still existing pin and socket and edge card products. A surface mount connector having a 2.54 mm footprint has terminals adapted to be soldered to conductive pads spaced 2.54 mm from the center line of one pad to the center line of an adjacent pad on a circuit assembly. Then 1.27 mm (0.05 inch) center line products emerged and the trend toward miniaturization was established. In response to the lastest needs of the telecommunication and personal computer industries, a 1.0 mm (0.039 inch) connector offering is emerging.
One such connector product line having a 1.0 mm (0.039 inch) footprint is referred to as the Conan Product line which includes low profile surface mount receptacles and headers for interconnecting parallel printed circuit boards as illustrated in FIG. 1. Such Conan connectors are commercially available from Berg Connector Systems, Inc., with offices in Valley Green, Pa.
More specifically, FIG. 1 shows a Conan header 10 in a mating position with respect to a Conan receptacle 12. The header 10 comprises an insulative housing 14 having a plurality of passages and a plurality of blade-like terminals 18, one of the terminals 18 extending through each of the passages. Tails 20 of the blade-like terminals 18 are illustrated solderable to pads 22 on a first printed circuit board 24. The receptacle 12 comprises an insulative housing 26 having a plurality of passages and a plurality of cantilever beam terminals 30, one of the cantilever beam terminals 30 extending through each of the receptacle passages. Tails 32 of the cantilever beam terminals 30 are illustrated solderable to pads 34 on a second printed circuit board 36 which is parallel to the first printed circuit board 24. Contact portions of the blade-like terminals 18 engage contact portions of the cantilever beam terminals 30 and, thus, function to electrically interconnect the first and second printed boards 24,36.
In most cases, the typical mode of mating two boards is by hand, even though the board assembly and soldering operations are highly automated. The connectors often also function as the mechanical feature that locks the two boards together and maintains the spacing between the two boards. When used to lock two boards together, the pressure and friction force of the contact portions of the blade-like terminals against the contact portions of the cantilever beam terminals is what mechanically holds the first printed circuit board to the second printed circuit board in the mating position illustrated in FIG. 1. However, this friction or withdrawal force is often insufficient to hold the boards together. Further, many blade-like terminals, including the ones illustrated in FIG. 1, have insertion ramps or inclined insertion ends 38 which are designed to faciliate insertion of the header 10 into the receptacle 12, but which also cause the receptacle 12 to be pushed away or ejected from the header 10 once the contact portions of the cantilever beam terminals 30 have been pulled across a flat region of the blade-like terminals 18 and reach the insertion ramps 38 of the blade-like terminals 18. It has also been noticed that when the contact portions of the cantilever beam terminals 30 are withdrawn from the mated position (illustrated in FIG. 1) onto the ramps or inclined ends 38 of the blade-like terminals 18, the force tending to eject the header 10 from the receptacle 12 is greater when the header 10 is being rotated, such as, in the direction of arrow A in FIG. 2, than when the header 10 is withdrawn along a straight line, such as, in the direction of arrow B in FIG. 3. Although less force is required to uncouple the connectors illustrated in FIG. 2, a small accidental movement of the boards 24,36 may cause uncoupling of the connectors 10,12 and the boards 24,36 in either the situation illustrated in FIG. 2 or the situation illustated in FIG. 3.
Active latching of the two connectors together isn't a practical solution to this problem because there isn't room to disengage latches. Other board mounted components in close proximity frequently pose problems to using active latches.
Thus, there is a need to increase the unmating force without significantly increasing the insertion force of conventional blade-like terminals with respect to cantilever beam terminals in connector assemblies to increase resistance to accidental unmating.